Fixed deposit

Dear Sir, i have my own small business, in which i am accepting amount from individuals and giving them 30% annual fixed returns. Currently i have 20 clients those are my relatives and colleagues and i am offering them MOU as security ....But now i want to expand my business and i have appointed agents.. i am getting many enquires. i may have around 5000+ clients base. so my question is .. 1) can i form proprietorship or pvt ltd company. 2) in mou shall what shld i mention received towards loan / fixed deposit / investment 3) can i issue share certificate / fixed deposit certificate.. 4) can i issue Fixed deposit certificate as i am accepting amount from them for fixed tenure. 5) what will be the minimum charges to form pvt ltd company.. what will be best and easiest way to start my businenss..